Polyoma BK virus (BKV)-associated nephropathy (PVAN) is a relevant cause of poor renal allograft survival.In a prospective analysis, we monitored BKV DNA in blood and urine samples from 62 consecutive pediatric kidney recipients. In patients with BKV replication, we analyzed the impact of reduction of maintenance immunosuppression on viral load kinetics and PVAN in patients with BKV replication. BKV-specific immunity was concomitantly evaluated on blood samples of viremic patients, by measuring the frequency of BKV-specific interferon-c -producing and cytotoxic T cells, and BKV IgG antibody levels. At a median follow-up of 24 months, BK viruria was observed in 39 of 62 patients, while BK viremia developed in 13 patients (21%). In all viremic patients, immunosuppression reduction resulted in the clearance of viremia, and prevented development of PVAN, without increasing the rate of acute rejection or causing graft dysfunction. As a consequence of immunosuppression adjustment, an expansion of BKV-specific cellular immunity was observed that coincided with viral clearance. We conclude that treating pediatric kidney transplant patients pre-emptively with immunosuppression reduction guided by BKV DNA in blood is safe and effective to prevent onset of PVAN. BKV-specific cellular immunity may be useful to guide this intervention.

The emerging role of humoral immunity in the pathogenesis of chronic allograft damage has prompted research aimed at assessing the role of anti-HLA antibody (Ab) monitoring as a tool to predict allograft outcome. Data on the natural history of allografts in children developing de novo Ab after transplantation are limited. Utilizing sera collected pretransplant, and serially posttransplant, we retrospectively evaluated 82 consecutive primary pediatric kidney recipients, without pretransplant donor-specific antibodies (DSA), for de novo Ab occurrence, and compared results with clinical-pathologic data. At 4.3-year follow up, 19 patients (23%) developed de novo DSA whereas 24 had de novo non-DSA (NDSA, 29%). DSA appeared at a median time of 24 months after transplantation and were mostly directed to HLA-DQ antigens. Among the 82 patients, eight developed late/chronic active C4d+ antibody-mediated rejection (AMR), and four C4d-negative AMR. Late AMR correlated with DSA (p < 0.01), whose development preceded AMR by 1-year median time. Patients with DSA had a median serum creatinine of 1.44 mg/dL at follow up, significantly higher than NDSA and Ab-negative patients (p < 0.005). In our pediatric cohort, DSA identify patients at risk of renal dysfunction, AMR and graft loss; treatment started at Ab emergence might prevent AMR occurrence and/or progression to graft failure.

Bortezomib is an effective inhibitor of neuroblastoma cell growth and angiogenesis. These findings provide the rationale for further clinical investigation of bortezomib in pediatric neuroblastoma.

Our findings suggest that third-party MSC are able to suppress allo-specific antibody production in vitro, and may therefore help overcome a positive cross-match in sensitized transplant recipients.

These authors contributed equally to this work.Alloantibody-mediated graft injury is a major cause of kidney dysfunction and loss. The complementbinding ability of de novo donor-specific antibodies (dnDSAs) has been suggested as a prognostic tool to stratify patients for clinical risk. In this study, we analyzed posttransplant kinetics of complementfixing dnDSAs and their role in antibody-mediated rejection development and graft loss. A total of 114 pediatric nonsensitized recipients of first kidney allograft were periodically monitored for dnDSAs using flow bead assays, followed by C3d and C1q assay in case of positivity. Overall, 39 patients developed dnDSAs, which were C1q + and C3d + in 25 and nine patients, respectively. At follow-up, progressive acquisition over time of dnDSA C1q and C3d binding ability, within the same antigenic specificity, was observed, paralleled by an increase in mean fluorescence intensity that correlated with clinical outcome. C3d-fixing dnDSAs were better fit to stratify graft loss risk when the different dnDSA categories were evaluated in combined models because the 10-year graft survival probability was lower in patients with C3d-binding dnDSA than in those without dnDSAs or with C1q + /C3d À or non-complement-binding dnDSAs (40% vs. 94%, 100%, and 100%, respectively). Based on the kinetics profile, we favor dnDSA removal or modulation at first confirmed positivity, with treatment intensification guided by dnDSA biological characteristics.

Progressive multifocal leukoencephalopathy (PML) associated with polyomavirus JC (JCV) infection has been reported to be usually fatal in allogeneic hematopoietic SCT (HSCT) recipients. We present the case of a 19-year-old HSCT patient diagnosed with JCV-associated PML after prolonged immunosuppression for severe GVHD. No short-term neurological improvement was observed after antiviral treatment and discontinuation of immunosuppressive therapy. Donor-derived JCV Ag-specific CTLs were generated in vitro after stimulation with 15-mer peptides derived from VP1 and large T viral proteins. After adoptive CTL infusion, virus-specific cytotoxic cells were shown in the peripheral blood, JCV-DNA was cleared in the cerebrospinal fluid and the patient showed remarkable improvement. Adoptive T-lymphocyte therapy with JCVspecific CTLs was feasible and had no side effects. This case suggests that adoptive transfer of JCV-targeted CTLs may contribute to restore JCV-specific immune competence and control PML in transplanted patients.

Polyomavirus BK-associated nephropathy (PyVAN) is the main infectious cause of allograft damage after kidney transplantation. A number of studies revealed an association between the presence of BKV-specific cellular immunity and BK viral clearance, with patients failing to recover specific T cells progressing to PyVAN. Evolution to allograft dysfunction can be prevented by restoration of BKV-specific immunity through a stepwise reduction of maintenance immunosuppressive drugs. Prospective monitoring of BK viral load and specific immunity, together with B-cell alloimmune surveillance, may allow a targeted modification/reduction of immunosuppression, with the aim of obtaining viral clearance while preventing graft injury due to deposition of de novo donor-specific HLA antibodies and late/chronic antibody-mediated allograft injury. Innovative, immune-based therapies may further contribute to BKV infection prevention and control.

Uncontrolled BK polyomavirus (BKPyV) replication in kidney transplant recipients (KTRs) causes polyomavirus‐associated nephropathy and allograft loss. Reducing immunosuppression is associated with clearing viremia and nephropathy and increasing BKPyV‐specific T cell responses in most patients; however, current immunoassays have limited sensitivity, target mostly CD4+ T cells, and largely fail to predict onset and clearance of BKPyV replication. To characterize BKPyV‐specific CD8+ T cells, bioinformatics were used to predict 9mer epitopes in the early viral gene region (EVGR) presented by 14 common HLAs in Europe and North America. Thirty‐nine EVGR epitopes were experimentally confirmed by interferon‐γ enzyme‐linked immunospot assays in at least 30% of BKPyV IgG–seropositive healthy participants. Most 9mers clustered in domains, and some were presented by more than one HLA class I, as typically seen for immunodominant epitopes. Specific T cell binding using MHC class I streptamers was demonstrated for 21 of 39 (54%) epitopes. In a prospective cohort of 118 pediatric KTRs, 19 patients protected or recovering from BKPyV viremia were experimentally tested, and 13 epitopes were validated. Single HLA mismatches were not associated with viremia, suggesting that failing immune control likely involves multiple factors including maintenance immunosuppression. Combining BKPyV load and T cell assays using immunodominant epitopes may help in evaluating risk and reducing immunosuppression and may lead to safe adoptive T cell transfer.